<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<p>
- CopyOnWriteArrayList
dung sych ArrayList thi rat la ton kem bo nho
va khi duyet thi phai dong bo het dan den toc do cham
 khi co 1 vai luong thay doi arraylist, va nhieu luong dang doc no
 => CopyOnWriteArrayList dung trong truong hop nay
 xem vi du de phan biet ArrayList va CopyOnWriteArrayList

 ve co ban luc iterator, thi thang iterator da copy thang arraylist ra roi
 nen trong luc duyet add element vao arraylist cung ko gay ra loi
 - ConcurrentMap la an toan hon ca 1 map da duoc synch
ho tro phuong thuc  putIfAbsent

- Semaphone
dieu tiet so luong thread dang mo voi 1 tai nguyen cu the (cho 1 so thread nhat dinh truy cap tai nguyen tai cung 1 thoi diem)
</p>
</body>
</html>